U.S. Pat. No. 8,864,311 discloses an illumination device including a light source formed from an arrangement of a plurality of switchable tiny light sources.
What is disadvantageous about the illumination device is that, for different illumination variants, an optimum illumination quality is not achievable in every case. When a rigid diaphragm is introduced into the illumination beam path, the diaphragm aperture is usually adapted to the maximum size of the light source in order to achieve a sharp imaging of the light source in an object region to be illuminated. When the size of the light source is reduced, an imaging of the light source, in particular of the edges of the light source, in the object region to be illuminated is then less sharp. Possible image aberrations of an illumination optical unit can have a more pronounced effect. Stray light or reflex light arising through the illumination optical unit or through mounting edges of optical elements is imaged into the object region. The illumination quality becomes poorer overall.
When a variable diaphragm is used, the size of a diaphragm aperture can be adapted to the size of the illumination light source. However, the outlay for a variable diaphragm aperture and the control thereof is high. The use of transmissive diaphragms, for example liquid crystal displays, is technically complex and results in losses of light. This is disadvantageous in the case of small light sources having limited light power.